For example, a display device such as a liquid crystal display device includes a display panel which has a pixel, and an illumination device such as a backlight which illuminates the display panel. The illumination device includes a light source which emits light, and a light guide to which the light from the light source is emitted. The light from the light source enters the light guide from a side surface, travels through the light guide, and exits from an emission surface which corresponds to one main surface of the light guide.
If the brightness of the emission surface of the light guide is uneven, the quality of an image displayed by the display panel may be degraded. For example, if the viewing angle of the light emitted from the light source is narrow, desirable brightness may not be produced in an area near the light source on the emission surface of the light guide. In this case, light having sufficient intensity cannot be supplied to the display panel in the area near the light source on the emission surface.